Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 260915 AFDOKX Area Forecast Discussion National Weather Service New York NY 515 AM EDT FRI AUG 26 2016 .SYNOPSIS... A weak front moves through the region late today followed by high pressure through the weekend. A cold front slowly moves through Monday and stalls nearby into Tuesday before dissipating. Another cold front passes through Wednesday night. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Band of showers/isolated thunderstorms across Upstate NY and eastern PA continues to weaken as it approaches. This activity is associated with a shortwave between 850 and 700 hPa and a prefrontal trough. Cannot rule out an isolated shower with possibly a rumble of thunder with the shortwave and prefrontal trough this morning. The prefrontal trough passes through much of the area by afternoon, but may linger across eastern Long Island and southern Connecticut. Instability is lacking today and moisture is not impressive. The lingering prefrontal trough could spark off a few showers, mainly across southern Connecticut and eastern Long Island. Rising heights aloft in the afternoon from a strong upper level anticyclone will create a cap around 15kft. This will likely prevent any convection from getting deep enough for much lightning activity. Did not go higher than slight chance with PoPs due to the inhibiting factors described above. The other concern for today is the hot temperatures and humidity. Have gone closest to the warmer MET/ECS guidance for highs today. This gives readings in the upper 80s and lower 90s, highest across the NYC metro, NE NJ, and interior. Dew points will start the day in the lower 70s, but should mix out into the upper 60s in the afternoon as the flow goes more to the west and northwest with the passage of the prefrontal trough. These lower dew points will occur during peak heating, preventing heat indices from rising above the upper 90s across NYC metro and urban NE NJ. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... A weak front will move through this evening with high pressure building over the area tonight into Saturday. The biggest change with this front will be the dew points as they will fall into the lower 60s tonight and remain there through Saturday with some spots falling into the upper 50s. It will still be hot on Saturday as the strong middle and upper anticyclone meanders across the middle Atlantic. High temperatures several degrees above normal in the middle and upper 80s are forecast. A few spots could touch 90 across Urban NE NJ/NYC metro. With the lower dew points, heat index values will be close to actual air temperatures. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... With the exception of the NAM...00z NWP model suite is in good agreement across North America at H5 into the middle of next week. The NAM is more amplified than remaining guidance...especially with the northern stream trough tracking through southeast Canada and northern New England Sun/Mon. The strong midlevel anticyclone over the Mid Atlantic Sat night will weaken and drift into the Tennessee Valley early to mid next week. Differences also become apparent with the pattern at the end of the period. While the 00z EC has trended more towards the GFS in developing a cutoff low over SE Canada...there are timing and strength discrepancies. However...this general pattern would re-introduce us to early fall-like weather. At the surface...high pressure encompassing New England Sat night...will move offshore on Sun. Another sunny day although onshore flow will limit mixing...especially at the coast with slightly lower max temps. Highs across urbanized NY/NY and areas N and W should range from mid to upper 80s...with lower to mid 80s common at the coast. Weak low pressure will track from the Great Lakes Sat night to northern New England by Mon morning. The associated warm front lifts north late Sun/Sun night with a waa pattern ensuing. Warmer temps and humidity returns on Mon as a cold front slowly moves through from the northwest. Not much pcpn expected as the majority of the upper level dynamics passes well to the north and the front runs into strong subsidence. The front then stalls nearby with perhaps a few showers Tue and Wed in response to ripples of vort energy and a few passing jet streaks aloft. Temps will be similar Tue and Wed as there is really no change in airmass behind the boundary. A somewhat stronger cold front passes Wed night...although again moisture appears limited. Have kept the forecast dry after Mon Night as a result. There will be a noticeably drier and somewhat cooler airmass behind this boundary. && .AVIATION /09Z FRIDAY THROUGH TUESDAY/... A cold front over the eastern Great Lakes this morning preceded by a pre-frontal trough across eastern PA will slowly track across the area today. The cold front will pass through the terminals from around 17Z northwest to 00Z east. There may be a few showers or even an isolated thunderstorm this morning with the pre-frontal trough and then again with the cold frontal passage this afternoon. Coverage of showers and thunderstorms is expected to be sparse with a low chance, so not included in the TAFs at this time. S-SW flow increasing to around 10 kt today will shift to the NW with the cold frontal passage this afternoon into early this evening. Winds will then continue to veer around to the N tonight at less than 10 kt. Brief MVFR conditions possible this morning before the onset of daytime heating, mainly at the coastal terminals. ...NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component forecasts, can be found at: KJFK TAF Comments: Timing of wind shifts may vary by as much as 2 hours. KLGA TAF Comments: Timing of wind shifts may vary by as much as 2 hours. KEWR TAF Comments: Timing of wind shifts may vary by as much as 2 hours. The afternoon KEWR haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KTEB TAF Comments: Timing of wind shifts may vary by as much as 2 hours. KHPN TAF Comments: Timing of wind shifts may vary by as much as 2 hours. KISP TAF Comments: Timing of wind shifts may vary by as much as 2 hours. .Outlook for 06Z Saturday through Tuesday... .Tonight through Sunday...VFR. .Monday into Monday Night...VFR. Potential cold frontal passage with a few showers and thunderstorms. .Tuesday...VFR. && .MARINE... A weak front moves across by this evening with high pressure returning tonight into Saturday. Sub advisory conditions are expected on all waters. Sub-advy conds prevail through the day Monday. However, potential remains for long period SE tropical swells on the ocean from through at least Tuesday. As a result...seas could build to 5-6 ft from late Monday through Tuesday night. && .HYDROLOGY... No significant widespread precipitation is expected through next week. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...24/DS NEAR TERM...DS SHORT TERM...DS LONG TERM...24 AVIATION...DW MARINE...24/DS HYDROLOGY...24/DS is the U.S. government's official web portal to all federal, state and local government web resources and services.